The quantitative determination of analytes in body fluids is of great importance in the diagnoses and maintenance of certain physiological abnormalities. In particular, it is important that diabetic individuals frequently check the glucose level in their body fluids to regulate the glucose intake in their diets. The results of such tests can be used to determine what, if any, insulin or other medication needs to be administered. In one type of blood-glucose testing system, test sensors are used to test a sample of blood.
A test sensor contains biosensing or reagent material that reacts with blood glucose. The testing end of the test sensor is adapted to be placed into the fluid being tested, for example, blood that has accumulated on a person's finger after the finger has been pricked. The fluid is drawn into a capillary channel that extends in the test sensor from the testing end to the reagent material by capillary action so that a sufficient amount of fluid to be tested is drawn into the test sensor. Alternatively, the person could apply a drop of blood to the test sensor that contains biosensing or reagent material that reacts with blood glucose.
Two reagents that are commonly used to determine glucose concentration are glucose dehydrogenase (GDH) and glucose oxidase (GO). Types of glucose dehydrogenase that may be used are pyrroloquinoline quinone glucose dehydrogenase (PQQ-GDH) and NAD-dependent glutamate dehydrogenase (NAD-GDH). PQQ-GDH is generally a stable reagent, but one disadvantage of PQQ-GDH is its cross-reactivity with maltose, which may be problematic with certain individuals. NAD-GDH tends to be less stable than PQQ-GDH and currently is more costly than either glucose oxidase or PQQ-GDH.
Glucose oxidase is currently not an expensive reagent, especially compared to NAD-GDH. In addition, glucose oxidase is generally a stable reagent and typically is more stable than PQQ-GDH and NAD-GDH. One disadvantage of using a glucose oxidase in a test sensor, however, is its sensitivity to the oxygen level in, for example, a blood sample to be tested. In determining the glucose concentration using glucose oxidase in a blood sample, the oxygen effect may sometimes be as great as 20%.
It would be desirable to use a test sensor with glucose oxidase that corrects for the oxygen effect and, thus, results in making more accurate glucose measurements. It would also be desirable to use a test sensor with other reagents that corrects for the oxygen effect and, thus, results in more accurate analyte measurements.